Biomimetic moth-eye nanostructures fabricated by nanosphere lithography in ZnSe enhancing transmission in the mid-infrared

Abstract

ZnSe is a highly regarded material for optical windows in the infrared spectrum, where transmission efficiency is a critical factor. Traditional surface antireflective coatings have limitations that can be overcome with biomimetic moth-eye nanostructures. In this paper, we present a novel method using nanosphere lithography with polystyrene (PS) nanosphere to fabricate moth-eye nanostructures (MENS) on ZnSe surface with an exceptional antireflection effect. The parabolic profile MENS, which is challenging to fabricate through conventional methods, was directly obtained using our dry etch process. This profile outperformed other shapes like circular cones, resulting in better antireflective performance. Our experimental results matched perfectly with the modeling and demonstrated that the MENS had broadband antireflection performance in the 2–5 μm wavelength range. The maximum transmission of MENS was 82.6%, which was a significant improvement over the flat ZnSe with 71.28% transmission, achieving a 17.2% transmittance enhancement that is close to the ZnSe transmission limit. Moreover, the MENS exhibited a highly desirable hydrophobicity with a wetting angle of 114° instead of 71° on flat ZnSe. Our work displays great potential in optoelectronic devices and high-power laser applications.